I was wondering if I needed an RO filter for my discus, and if I do, what is a good one and how much does it cost? Also, to the best of my knowledge, RO water is water that's been passed through a membrane that removes every single thing in the water like salt ions. Is this correct and can someone give me a better description of what exactly a RO filter does?

ro removes pretty much everything, never use ro neat, always mix with a ratio that suits of dechlorinated tapwater, i use a 70/30% or 50/50 mix to get my nitrates down as the tap is 50+ppm, it will lower ph also, i use a 3 stage 50gpd, depending on the temps of the water depends on the flow, cold=slower, takes about 1 1/2 hours for 10 litres and the water cold as its winter,
tapwater does contain good minerals so that us why you mix, ro will remove the good too.
it all depends on the source water and its parameters to warrant using ro, i do because of nitrates like i said, if you have 7-8ph, 0 ammo, 0 nitrites and a 30ppm or below nitrates then maybe save your money and be grateful to your water company
it is a slow process so it dont end at the filters, you need the shut off kit as if you forget about it you get a flooded kitchen like i have a couple of times
would have it fill a camping/caravan tank so you have a supply ready rather than fill separate containers like i do, that will change in new year when i get 70L container (cant wait) and use the shut off kit with that and no floods
mine is a V2Pure 50 that comes with the tds meter, if you get one with a higher output per day it will output water faster but then the filters will cost you more, if you use a tank to store it dont matter so much, depends how much you are likely to use.

here in cleveland we have moderately hard water out of the tap and a PH of about 7.0-7.2...many here raise and breed discus in straight tap water....
something that a lot of people do not realize about RO filters is that for every gallon of RO water you get into a container ; 3-5 gallons of water go down the drain....that is a very considerable amount of waste.....and loss of money..

yup, sorry forgot to mention, 3/4 or there abouts goes straight down the drain unless you collect it in a large drum, it has no use except for watering the garden and NOT food i might add, it is not fit for anything to do with human consumption, thankfully i am not on a water meter otherwise i would think twice about having one and buy the ro from the shops.
if you collect ro from the shops, always use a food grade container that you purchased and know the history of so you know what has been carried inside it.

yup, sorry forgot to mention, 3/4 or there abouts goes straight down the drain unless you collect it in a large drum, it has no use except for watering the garden and NOT food i might add, it is not fit for anything to do with human consumption, thankfully i am not on a water meter otherwise i would think twice about having one and buy the ro from the shops.
if you collect ro from the shops, always use a food grade container that you purchased and know the history of so you know what has been carried inside it.

Better idea is just to buy a new 100g water drum that can be gotten just about anywhere brand new, cleaned and made safe for storage.

Transport with 5g cleaned chlorine containers that are used with pools. Just buy brand new and clean the same way.

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There are also float style - cut off valves for about $5. They're kinda like the ball in your toilet tank (only a lot smaller). So when it hits a certain level, it turns everything off.

I don't think anybody addressed price. RO units are rated in GPD - gallons per day and typically sell for about $1 per GPD. There are units that are up to 5 stage that also have DI stages...which is a DeIoniser. RO/DI will take your water to almost pure H2O. You definetely want to mix that water...as Weedkiller suggested.

So pricewise - # of stages - what type of stages - GPD - and if it has a water pressure gauge on it...all come into play. There are also boosters to increase water pressure.

Do you need RO for discus? A lot depends on your water parameters. Around here (Chicago) most discus breeders use RO for breeding, and straight tap or RO wastewater, for growout. One breeder insists that the extra minerals in the RO wastewater increases his growth rate with younger discus. The RO for breeding aids in parental slime forming on breeders and disolving the egg membrane when hatching.

I did address the outputs and i have the shut off kit, just waiting till i can get a 50L container fitted under my stairs then ill add the ball valve.. use a tap valve to shut it off at the mo and set a timer to remind me.. have a few forgetful spillages lol

ro water is awsome! once you start making your own water you will never go back! consider this insted of mixing tap water with your ro water go to a good lfs and get some water buffers. personally I use Florin delta KH+ and florin delta GH+. buy a 5 gallon bucket and make mix's till you find the one you like. personally I use a 30gallon res that has a pump in it that hook a hose up to to pump my water out and take the hose off to have it just stir up the water. also benefit of making your own water all the way around is while the city screws around with your tap water your ro will always be the same, also they cost about $300 around here for a cheep one.

consider this insted of mixing tap water with your ro water go to a good lfs and get some water buffers. personally I use Florin delta KH+ and florin delta GH+. buy a 5 gallon bucket and make mix's till you find the one you like.

sorry should be more specific. make mixes of the two until you find the right mix for your water parameters you want have. sounds complicated but once you get it right you will ALWAYS know what is in your water unless you let other ppl touch the tank

can add buffers if you like but the tap water mix is a far cheaper and easier option and does the job fine, not one to keep throwing chems in my tanks if i dont need too.
only thing i add is r.o tap mix, api stress coat and salt and so far (touch wood) everyone seems happy

thats funny cause the chems you add means no hauling any water just a scoop and not to mention your just adding back to the water only what the fish need and as for cheeper you save like 10 bucks mixing

I have very very hard tap water, so I just buy the RO water in 3gal jugs from the grocery store, and add with some tap and some stresscoat. The RO water is cheap, especially when you use the refillable containers, and works well for me. When I have to top off the tank, (very low humidity here causes evaporation) I pour RO water in straight from the jug. like Weedkiller, I try not to add chemicals unless I absolutely have no choice. In the years past, I did use tank additives more, but found out from experience that one slip up (mis-measure, old stuff, whatever) could be disastrous! Now, I like the natural route. I looked into a RO filter, but with the initial expense, and waste water, It seemed less hassle to just buy the RO. I keep 4-5 jugs in my basement, in case I need it.

Whos hauling? I own an r.o filter and recommend anyone else to do the same.
If you did have to haul then x2 25L containers is not to bad if you have transportation.
With chems you are always messing around adding this adding that to compensate. With r.o you get pure filtered water and with added tap water you get the rest